University of Bordeaux, CIRID, UMR 5164, F-33000 Bordeaux, France.
Development. 2013 Aug;140(16):3311-22. doi: 10.1242/dev.091082. Epub 2013 Jul 17.
Pluripotent mouse embryonic stem cells (mESCs), maintained in the presence of the leukemia inhibitory factor (LIF) cytokine, provide a powerful model with which to study pluripotency and differentiation programs. Extensive microarray studies on cultured cells have led to the identification of three LIF signatures. Here we focus on muscle ras oncogene homolog (MRAS), which is a small GTPase of the Ras family encoded within the Pluri gene cluster. To characterise the effects of Mras on cell pluripotency and differentiation, we used gain- and loss-of-function strategies in mESCs and in the Xenopus laevis embryo, in which Mras gene structure and protein sequence are conserved. We show that persistent knockdown of Mras in mESCs reduces expression of specific master genes and that MRAS plays a crucial role in the downregulation of OCT4 and NANOG protein levels upon differentiation. In Xenopus, we demonstrate the potential of Mras to modulate cell fate at early steps of development and during neurogenesis. Overexpression of Mras allows gastrula cells to retain responsiveness to fibroblast growth factor (FGF) and activin. Collectively, these results highlight novel conserved and pleiotropic effects of MRAS in stem cells and early steps of development.
多能性的小鼠胚胎干细胞（mESCs），在白血病抑制因子（LIF）细胞因子的存在下维持，提供了一个强大的模型，用于研究多能性和分化程序。对培养细胞的广泛基因芯片研究导致了三个 LIF 特征的鉴定。在这里，我们关注肌肉 ras 癌基因同源物（MRAS），它是 Ras 家族的小 GTPase，编码在多能基因簇内。为了研究 Mras 对细胞多能性和分化的影响，我们在 mESCs 和非洲爪蟾胚胎中使用了增益和功能丧失策略，其中 Mras 基因结构和蛋白质序列是保守的。我们表明，mESCs 中 Mras 的持续敲低降低了特定主基因的表达，并且 MRAS 在分化过程中 OCT4 和 NANOG 蛋白水平的下调中起着关键作用。在非洲爪蟾中，我们证明了 Mras 有潜力在发育的早期阶段和神经发生过程中调节细胞命运。Mras 的过表达允许原肠胚细胞对成纤维细胞生长因子（FGF）和激活素保持反应性。总之，这些结果突出了 MRAS 在干细胞和发育早期阶段的新的保守和多效性作用。
